I am the owner of an older 3.0 liter diesel car and winter mornings are quite painful for both me and the car. Even though thermostat is fine, heating takes forever. I know diesel only heats up while driving, but since my daily route is very short, I arrive at work with the temperature gauge still in the blue area, even though I let it run for 5-10 minutes before taking off. While this is very bad to the engine, it's also very uncomfortable for the passengers.
I am thinking of building an intake air heater to run it for a few minutes after starting the car, an arduino controlled DIY with a few cheap chinese heating elements and a build solid and responsible enough to avoid setting the car on fire obviously.

I'm ok with waiting 5 minutes for the car to heat up, as long as it does heat and defrost in this period.

Are there any drawbacks to this approach? I don't see this being a common thing anywhere. Will it confuse the ECU, because the external temperature sensor will read like -10 while the intake will read +30?
is there anything else to take into account before starting this build?

What will be the total power (in Watts) of the heaters that you are planning to use?
– HandyHowieJan 15 at 10:09

I'm planning to stay in the 200-300w range to avoid putting load on the alternator and draw the battery. I'll perform some measurements once my heating elements arrive. I ordered this s.click.aliexpress.com/e/bHCZ6b1O and it gets burning hot in seconds. Six of these will be below 200w so it should be fine
– NickJan 15 at 10:15

I would be very surprised if 300w warmed your car significantly. Have you looked into purchasing a diesel burning heater as fitted to some luxury cars - webasto-comfort.com/en-uk/heating These give heat output in kWs.
– HandyHowieJan 15 at 11:18

As I said I'm not looking to heat the car itself, but increase the combustion temperature, which will heat the car faster than it currently does. My car had a stock webasto which of course doesn't work even though I've spent a lot of time fixing it
– NickJan 15 at 11:26

I have just read your text again and it isn't clear that you are asking to heat the air going into the engine.
– HandyHowieJan 15 at 12:09